1. Field of the Invention
The present invention relates to transflective liquid crystal display devices, and more particularly to a transflective liquid crystal display device of an in-plane switching type or a vertical alignment type.
2. Description of the Related Art
Transflective liquid crystal display devices each having a transmissive part and a reflective part in one subpixel are used as display units for mobile devices.
Such transflective liquid crystal display devices use a system in which electric fields are applied to liquid crystals held between a pair of substrates in a direction normal to the planes of the paired substrates to drive the liquid crystals. In this case, to match the characteristics of the transmissive part and the reflective part, a level gap is provided between the transmissive part and the reflective part, and further a phase differential plate is arranged between a polarization plate and the liquid crystal layer.
On the other hand, IPS type transflective liquid crystal display devices are also known, in each of which pixel electrodes (PIX) and counter electrodes (CT) are formed over the same substrate, and gray scale levels are controlled by applying electric fields to these liquid crystals by rotating them within the substrate plane. For this reason, these devices have a significant feature that the relative shades of the display image are not reversed when the screen is looked at askew. To take advantage of this feature, it is proposed to structure a transflective liquid crystal display device by using an IPS type liquid crystal display device.
However, structuring a transflective liquid crystal display device by using an IPS type liquid crystal display device involves a problem (1) that, when the transmissive part is normally black, the reflective part becomes normally white, namely the relative shades are reversed between the transmissive part and the reflective part.
In view of this point, the present applicant has already applied for a patent on a transflective liquid crystal display device having a new pixel structure (see Japanese Patent Application No. 2005-322049) intended to solve this problem (1).
This transflective liquid crystal display device on which a patent is pending has a pixel structure for each subpixel in which an independent counter electrode for each of the transmissive part and the reflective part is provided against a common pixel electrode of the transmissive part and the reflective part, and reversal of the relative shades between them is prevented by applying different reference voltages (a counter voltage and a common voltage) to the transmissive part and the reflective part.
In the IPS type liquid crystal display device, the pixel electrode (PIX) is disposed on the liquid crystal side of one of the paired substrates. In this arrangement, a hole is bored in the counter electrode (CT), in which a contact hole is formed, and a driving voltage is applied to the pixel electrode (PIX) through this contact hole.
However, the transflective liquid crystal display device disclosed in Japanese Patent Application No. 2005-322049 involves a problem (2) that, in boring a hole in the counter electrode (CT) to apply a driving voltage to the pixel electrode (PIX) arranged on the liquid crystal side of one of the substrates and forming a contact hole therein, non-display parts increase and the transmissivity drops.
Therefore, to solve this problem (2), the present applicant has already applied for a patent on a transflective liquid crystal display device having a novel pixel structure (see Japanese Patent Application No. 2006-109659).
This transflective liquid crystal display device on which a patent is pending is intended to prevent the transmissivity from dropping by using the gap between opposing counter electrodes (CT) as the opening in the counter electrodes (CT) required for the formation of the contact hole.